They removed the option to buy the DLCs separately during the winter sale. Only way to get them now is to buy the GOTY version, which has a separate entry so you'll end up with 2 Batman Arkham City entries in your Steam library.

Not that I'd get this game anyway because of it's DRM, but this is one reason why I always wait for the Complete/GOTY edition to come out. Unfortunately they did the same thing with Arkham Asylum so folks should have seen it coming. If you really want all the DLC your best bet now would be to buy the GOTY and then ask Steam Support to remove the regular version from your library if the redundant entry bothers you.

I won't drop a whole 7.50$ just to get the remaining DLCs. I just found a shipment of Arkham asylum DLCs and they seem to work on legit steam copies according to some users. I might just get those instead, seriously disappointed.

I'm not aware of any gameplay problems, I just find it annoying to have duplicate versions of something I have there, especially having 'worse' versions. I avoid visual annoyance most of the time by using different categories (added 'dupes' to my trash category) but I still don't like thought that number of products in my library is kinda innacurate.

I'm in the exact same position. Only managed to get the Quinn DLC and missed out the rest. I think it's terrible that they fucked over the early people who bought the game. We should all get free upgrades to GOTY.